This invention relates to foamed insecticide compositions.
An insecticide is a compound used to kill or prevent the growth of parasite arthropods, such as insects and/or arachnids and/or crustacean; or a compound used to repel or prevent infestation by parasite arthropods, such as insects and/or arachnids and/or crustacean. Common infestations in humans include lice and scabies.
Infestation with lice is referred to as pediculosis. Lice are ectoparasites that live on the body. The 3 types of lice that parasitize humans are Pediculus humanus capitis (head louse), Pediculus humanus corporis (body louse), and Pthirus pubis (pubic louse).
Every year, between six and 12 million people in the United States, primarily children three to 10 years of age, are infested with head lice. Girls are at greater risk because they have more frequent head-to-head contact. Head lice affect people across the socioeconomic spectrum.
Scabies is an infestation of the skin with the microscopic mite Sarcoptes scabei. Infestation is common, found worldwide, and affects people of all races and social classes. Scabies spreads rapidly under crowded conditions where there is frequent skin-to-skin contact between people, such as in hospitals, institutions, child-care facilities, and nursing homes.
Occasionally, a skin infection develops following a bite. Scratching as a result of insect bites can damage the skin and allow bacteria to get in. Infection causes redness and tenderness around the bite, which may gradually spread, and sometimes can become serious.
Resistance of insects to pesticides is commonly known. For example, resistance of lice to 1 percent permethrin has been reported in the US and elsewhere. There are two broad mechanisms by which insect pests develop resistance to insecticides. They may produce large amounts of enzymes, such as esterases which either break down the insecticide molecule or bind to it so tightly that it cannot function (a process known as sequestration). The second mechanism involves mutation of the insecticide target site, such as the acetylcholinesterase enzyme in the nervous system. This effectively blocks the action of the insecticide. Both types of mechanism have been studied in various species of insect.
A common way to overcome resistance is to add a secondary active agent, which impedes that resistance mechanism. An example of such secondary active agent is piperony butoxide, which inhibits the ability of insects to degrade insecticides such as pyrethrum. Another approach is to add volatile solvents such as ethanol and propanol to the insecticide formulation.
U.S. Pat. No. 5,783,202 provides a pediculicidal mousse composition containing (a) from about 0.1 to about 10% w/w of a pediculicidal agent, preferably, pyrethrin, and, optionally from about 0.5 to about 15% w/w of a synergizer therefor, such as piperonyl butoxide, (b) about 70 to about 97% w/w of a foaming agent, which is preferably a quick breaking alcoholic foaming agent; and (c) from about 3 to about 20% w/w of an aerosol propellant.
A pediculocide mousse, which contains the active ingredients piperonyl butoxide (4%) and pyrethrum (0.33%) and the inactive ingredients cetearyl alcohol, isobutane, PEG-20 stearate, propane, propylene glycol, purified water, quaternium-52, SD Alcohol 3-C (26.5% w/w) is commercially available under the name “RID Lice Killing Mousse” (Bayer Corporation). However, this product possesses at least four disadvantages: (1) Irritability: due to the high alcohol content, the incidence of skin and eye irritation is high; (2) “Quick breaking” property: the foam is thermo-sensitive and breaks down rapidly at body temperature so that is cannot easily be spread manually throughout the scalp area; (3) Skin drying; and (4) Inflammability: 26.3% alcohol renders the foam inflammable. A test according to European Standard prEN 14851, titled “Aerosol containers—Aerosol foam flammability test” reveals that this product is inflammable.
Thus, the development of new formulations of permethrin, which will overcome these and other disadvantages, is warranted.
Furthermore, an easy to use product that addresses the frequent skin and eye irritation associated with pediculocide shampoo, cream rinses and lotions is highly desirable.